Pulverized-coal feeder



Aug. 12, 1930. F. F. FRICK 1,772,802

PULVERI ZED GOAL FEEDER Filed Jan. 20, 1928 Patented Aug. 12, 1936UNITED g STATES PATENT oFFlcE FEBICK F. FBIGK, OF ANAGONDA, MONTANA,ASSIGNOB T0 ANACONDA COPPER MINING COMPANY, OF ANACONDA, MONTANA.

PULVEBIZED-COAL FEEDER Y Application led January 20, 1928. Serial No.248,227.

This invention relates to an apparatus for feeding pulverized coal orother comminuted fuel into an air line or furnace wherein the pressureis above atmospheric pressure.

Pulverized coal is usua ly fed into furnaces and boilers throughcalibrated screws from bins. The coal drops from the screw into a streamof air which sweeps it into the furnace. The pressure on the coal as itfeeds into the screw is atmospheric plus the weight of the coal. Thepressure at the delivery end of the screw is atmospheric plus a fewounces of air pressure in most cases.

When it is desired'to feed pulverized coal into the tuyre pipes of afurnace like a copper converter or a blast furnace, so that the airblast will carry it into the furnace, a new problem is encountered. Ifan attempt is made to feed'the coal against the air pressure in thetuyre pipes, with an ordinary screw, the air pressure forces the coalback through the screw. This has been overcome in some cases by using ascrew choked near the delivery end. yThis choking may be obtained bydecreasing the pitch of the screw near the delivery end or decreasingthe clearance between the screw shaft and the housing near the deliveryend. The object of either scheme is to compress the coal in the screwnear the delivery end so that it will resist the back pressure of theair on the delivery end of the screw. The choked screw has givenreasonably good service in some cases particularly in the case of coalswhich are rather greasy and which tend to lubrlcate the screw. It hasbeen found, however, that this method of feeding coal is undependable.There is always a tendency, under varying cond1t1ons of physicalcharacter, fineness and wetness of the coal, etc., for the choked screwto bind or clog. Another disadvantage of the choked screw is the smallclearness necessar between the screw and the housing. Th1s smallclearance means more ower and more rapid wear of the screw and ousing.

It has been found that an ordinary unchoked screw with reasonableclearance between screw and housing can be used with entire satisfactionif provision is madei for maintaining the gas pressure on the feed endof the screw substantially e al to or greater than that at the deliveryend. The arrangement preferably is such that the ressures areapproximately the same on the feed and discharge ends of the screw. Theinvention will be described in detail by reference to the accompanyingdrawing which illustrates one form of apparatus embodying the same.

Referring to the drawing:

Fig. 1 is a vertical section through the apparatus, and

Fig. 2 is a vertical elevation of a modification of thatpart of theapparatus shown in Fig. 1 whichconnects the delivery end of the screwwith the tuyre pipes.

In the drawing, 1 1s an air tight tank or hopper for pulverized coalwhich is divided by partition 2 into two intercommunicatin compartments,the coal compartment 3 and an equalizing chamber 4. A coal char e pipe 5closed by a cover 6 is provided at t c top of the coal compartment. 7 isa pipe for supplying air under pressure to the tank 1. 8 is a screwwhich rotates in the housing 9 at the bottom of the coal compartment anddelivers into the equalizing chamber. 10 is a conduit for receiving thecoal falling from the delivery end of the screw and delivering it to theinjector 11 which forces it throu h the pipe `12 into the tuyre pipes oftie furnace.

Fig. 2 shows a modification of the apparatus of Fig. 1 in which theinjector 11 is omitted and a 90 curved pipe 13 is substituted therefor.

The Operation of the device is as follows. Pulverized coal is passedinto-.the coal compartment 3 through the charge pipe 5. The charge pipeis then sealed by means of the cover 6 or other suitable sealing means.The injector 11 is put into operation, airis supplied through the pipe 7which is connected to the air line giving the main supply of air to thetuyres, and the screw 8 is started to revolve. The coal is fed at a ratedepending upon the speed of revolution of the screw into the equalizingchamber from which it falls with the current of air flowing downwardlythrough chamber 4 into the conduit 10 and injector 11, whence it iscarried into the tuyres of the furnace which may be, for example, of theconverter type in which the air passes into a molten bath or of theblast furnace type. As stated heretofore, the pressure in the tank 1should be approximately equal to or greater than the pressure in the airline or tuyres to which the coal is delivered, i. e., the pressures onthe feed and dischar e ends of the screw are approximately alanced.

This device has given perfect satisfaction. There is no cloggin orbinding of the screw and no clogging o the injector. The coal deliveredfrom the injector is uniform Vin quantity and is well distributedthrough the air.

It has been found that the use of the injector 11 is not necessary andthat the device may be used with or without it. The injector simplyassists and assures the delivery of the coal into the tuyres. When theinjector is not used the best results are obtained by maintaining thepressure in the tank somewhat higher than the pressure in the tu res.

The primary object of the equa izing chamber is to equalize the pressureon both sides of the partition thus equalizing the pressure on both endsof the screw, and preventing choking of the screw. Another function ofthis chamber is to allow pressure to be put on the tank so that the sameor a slightly greater pressure can be maintained on the side of theinjector receiving the coal feed than is on the side of the injectorwhich delivers the coal to the tuyres. In this way a satisfactoryoperation of the injector is obtained and a system with practicallyuniform pressure is thus maintained. It is obvious that the principle ofmy invention, i. e., the

approximate equalization of the pressures on the feed and discharge endsof the screw, may be accomplished in various other ways, and thattherefore the invention is not limited to the precise apparatus hereindescribed except as is required by the terms of the appended claims.

The coal feeder described and illustrated herein is especially designedfor use in connection with the apparatus disclosed in an application ofUlysses A. Garred, Serial No. 181,979, but it may be used on varioustypes of furnaces and with any suitable pressures and quantities -ofair.

I claim:

l 1. An apparatus for feeding pulverized coal under pressure into thetuyre pipes of converter or blast furnaces comprising an air tighthopper divided into two intercommunicating compartments one of which isa coal compartment and the other an equalizing chamber, a pipe connectedto the hopper for supplying air thereto under pressure, a screw forfeeding the coal from the coal compartment into the 4equalizing chamber,a conduit connected to the bottom of the equalizing chamber forreceiving the coal and delivering it to the furnace.

2. An apparatus for feeding pulverized coal under pressure into thetuyre pipes of converter or blast furnaces comprising an air tighthopper divided into two intercommunicatmg compartments one of which is acoal compartment and the other an equalizlng chamber, a pipe connectedto the hopper for supplyiner air thereto under pressure, a screw forfeeding the coal from the coal compartment into the equalizing chamber,a conduit connected to the bottom of the equalizing chamber forreceiving the coal and an 1njector arranged to assist the deliver of thecoal from the said conduit into the urnace.

In testimony whereof, I aix my signature.

FREDERICK F. FRICK.

